Sound generating and sound responsive device



Nov. 24, 1931. H. F. FRUTH SOUND GENERATING AND SOUND RESPONSIVE DEVICE filed April 25, 1930 W My Patented Nov. 24, 1931.

UNITED STATES PATENT OFFICE HAL '11. FRU'I'H, OF RIVERSIDE, TLLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMIPANY, INCORPORATED, OF NEW YORK, NLY A CORPORATION OF NEW YORK SOUND GENERATING AND SOUND RESPONSIVE DEVICE Application filed April 25,

This invention relates to sound generating and sound responsive devices, and more particularly to receivers, transmitters and microphones of acoustic apparatus wherein a vibrating member is used in the reproduction, recording, analyzing and measuring of sound Waves and enforced vibrations.

An object of the invention is to provide an apparatus wherein the vibratory member 0 may be damped in such a manner as to insure a uniformly accurate and faithful reproduction of the in ipressedvibration over a wide range of frequencies.

In order to accomplish this and other obects, the vibratory member is provided with a mounting composed of a plurality of thin laminae each of which is deformed from a true plane into an irregular or crinkly surface, so that adjacent lamina contact with each other 9 only at spaced points with the result that a yielding air cushion is provided. Theirregular shape of the laminae is produced by dis tortional forces generated in the material itself during its manufacture, so that the laminae do not tend when in use to return to a plane shape, but retain their form and resiliency indefinitely. The material of the lam;- nae is also especially resistant to moisture and heat, with the result that the apparatus func- 30 tions efficiently even under conditions of high temperature and humidity.

The invention will be more fully understood from the following description'taken n connection with the appended drawings 1n. which .Fig. 1 is a sectional view of a telephone transmitter embodying the invention.

Fig. 2 is an enlarged sectional view of a portion-of the diaphragm mounting, and

Fig. 3 is a fragmentary perspectlve view of a plurality of laminae in superposed (positlon. The transmitter shown 'in the rawmgs comprises a diaphragm 10 of a common type, designed to be vibrated by the sound waves entering the transmitter, which vibrations 1930. Serial Iil'h. 447,202.

alternately compress and allow to expand a. quantlty of granular carbon or other microphonic material 12 contained in a button 14. The dlaphragm bears against an annular electrode 16 surrounding its central portion, a plurality of annular leaves or laminae 18 formed in accordance with this invention bemg interposed between the diaphra m and the electrode. At. its periphery, t e diaphragm is formed with a flanged ortion 20 which extends into a recess forme by annular members 22 and 2&1, and a lurality of annular laminae 26, 28formecl in accordance with this invention are interposed between portion 20 and the members 22 and 24. In order to facilitate assembly and retain the laminae in fixed position relative to each other perforations 30, 32 are punched through them so as to cause them to interlock.

The laminae 18, 26 and 28 are preferably formed by impregnating paper sheets of about .000 thickness with a phenolic condensation product dissolved in ethyl acetate or other suitable solvent, and drying and ouring the impregnated sheets without exerting pressure thereon, A suitable method of producing such'sheets is to pass a film of paper through an impregnating bath, then remove it I the excess impregnating material, and thence pass the film over a roller, subjecting it to 7 heat while it is passing to said roller to evaporate the solvent from the impregnating material. The film may then. be passed from said roller over a second roller, being sub jected to a higher degree of heat to cure it while passing from one roller to the other. The longitudinal tension on the film during the drying and curing operations .is sufiicient to drawvit through the impregnating bath and over the rollers, but does not prevent the paper from being deformed due to the internal stresses set up withinthe material of the film by the drying and curing operations, and there is no lateral tension on the paper and no transverse pressure, so that the paper may 90 and does assume a Wavy or crinkly form which admirably adapts it to the purpose in View. Since the impregnated paper is baked while in such crinkly form, it does not tend, under stress or age, to assume a plane shape. The laminae formed in accordance with this invention arealso especially resistant to heat and moisture, and retain their resilience indefinitely even under adverse temperature and humidity conditions.

The film of paper is then punched into circular rings or laminae 18, 26 and 28, a suitable number of such rings being superposed and held in fixed relation by means of the perforations 30, 32, preferably formed at the same time that the laminae are punched. The rings 26 and 28 are then placed in the transmitter so as to loosely fill the space between the mem bers-22 and 24:, where their crinkly shape causes them to separate, forming air pockets 34. The laminae thus form air cushions which act under the vibrations of the diaphragm to damp the vibrations thereof, the degree of damping being a function of the resiliency of the laminae, the number and thickness of the leaves, and the space provided between the members 22 and 24:.

The laminae 18 are also assembled in the transmitter in the relation shown in Fig. 1, where they function in a manner similar to that above described in connection with laminae 26 and 28.

While the invention has been specifically described in connection with a telephone during the curing of the impregnated pa er.

4. In telephone apparatus, a vibratory iaphragm, and a damping member for said diaphragm comprising a plurality of. superposed leaves of phenol resin impregnated material deformed into a crinkly contour by distortional stresses generated in the material of the leaves during the process of manufacture.

In Witness whereof, I hereunto subscribe my name this 19th day of April, A. D. 1930.

HAL F. FRUTH.

transmitter, it is obviously applicable to the damping of vibratory members in receivers contour formed by curing the impregnated paper.

2. In telephone apparatus, a vibratory member, a rigid member in spaced relation thereto, and a plurality of loosely mounted thin leaves between the vibratory member and prising a plurality of superposed leaves of paper impregnated with a phenolic condensation product, and deformed into a crinkly contour by stresses generated within the leaves 

